Reactions of trifluoro- and hexafluoroacetylacetones with thiobenzoylhydrazine

The reaction of thiobenzoylhydrazine with trifluoroacetylacetone leads to the product of condensation at the CH₃C=O bond with the 5-hydroxy-2-pyrazoline structure. The tautomeric transition to the 2,3-dihydro-1,3,4-thiadiazole isomer occurs in solution. This isomer undergoes the cleavage to 2-methyl-5-phenyl-1,3,4-thiadiazole and trifluoroacetone. The reaction of thiobenzoylhydrazine with hexafluoroacetylacetone affords one of diastereomers of 3,5-dihydroxy-3,5-bis(trifluoromethyl)pyrazolidin-1-yl](phenyl)thioketone, which at equilibrium is transformed in solution into the second diastereomer of the 3,5-dihydroxypyrazolidine form followed by the elimination of water elements and formation of a tautomeric 5-hydroxy-2-pyrazoline-2,3-dihydro-1,3,4-thiadiazole mixture.